diagnostic tools to trace the reason xruns are happening?

Hartmut Noack zettberlin at linuxuse.de
Sun Jun 5 21:09:16 UTC 2011

Am 05.06.2011 20:05, schrieb Ralf Mardorf:
> On Sun, 2011-06-05 at 19:39 +0200, Hartmut Noack wrote:
>> Am 05.06.2011 11:00, schrieb Robert Klaar:
>>> What happens if you set the frames/period settings higher? I have similar
>>> setup and can't get it to run on any lower than 1024 frames(if I want to
>>> avoid xruns), but then I've set the sample rate to 48000. I've never noticed
>>> any problems with the latency, it's at 46 or something now but I can't hear
>>> any difference between this and something lower, can you? .)
>> Yes I can.
>> I work with musicians and my experience is:
>> lower than 5ms: nobody noticed that in comparison with 10ms
>> 5-10ms: everything fine, no complaints
>> around 16ms: all but some singers realise that something is going on,
>> faces grow longer, some demand changes.
> Ok, so we do agree that the Haas-Effect has nothing to do with audible
> delay for a groove, but I don't agree that lower than 5 seconds isn't
> audible. It is, regarding to a groove, e.g. played by a MIDI keyboard,
> controlling a soft-synth. It's annoying, but a constant delay is
> something a musician is able to handle, anyway, I do agree that up to 11
> ms are 'quasi' inaudible. Pipe organs might have a delay up to 30 or 50
> ms, I dunno, but musicians are able to play such an instrument. Just
> jitter is a no go, especially for this case ...
>> For very big projects on lesser machines I run Jack with 30 or more ms
>> latency. It is OK for mixing/editing etc but I do not record any
>> overdubs with such settings.
> ...
> What's the problem with overdubs? You listen to the delayed sound, but
> for you it isn't delayed, you play in real-time without monitoring the
> delayed recording and the latency compensation moves it to the correct
> time.

The problem is, that I record most of the overdubs using software, that 
either generates or processes the signal.

> Hence latency has no impact, but jitter would have, because jitter
> can't be auto-compensated.

I use to record overdubs by playing instruments/voice so we would talk 
about audio-jitter here.

That would be:

If I record the very same audio-signal from a Jack-output to a track in 
Ardour several times it would be predictable, that the recordings start 
to be/sound affected by such jitter-effects.

How many generations do you estimate until such effects would become 

>> I remember I did some years ago but it
>> really was not fun and the results where not as good as they could have
>> been.
> I don't understand? What happened? Latency only will become an issue, if
> it isn't a fix delay, or if you need to monitor the delayed output, e.g.
> for soft synth,

exactly that, see above.

> apart from that latency has no influence.
>> Any recent Linux sould allow settings for 16ms or lower for normal load.
> It's related to the hardware and work flow. ElCheapo cards might be able
> to keep such latency when Periods/Buffer are set ex 3, jitter than might
> be another issue ;).

Yes, it is known, that cheap chipsets almost never provide exactly the 
samplerate they are set up with and that they can drift.
To be honest: I do not hear any effects of that.

Please correct me, if I am wrong: the soundcard is only the 
player/recorder. Jack processes the signal internally whithout using or 
even needing the sound card at all. Thus it is no great suprise, that 
material, that I process while Jack runs with a HDA-chipset fails to 
degenerate and sounds not better or worse if I play them the other day 
on a envy24-chipset or a Presonus Firebox.

I do hear the differences of a ADC/DAC for 30 Euros compared with a 
converter for 30 Cents ;-)

>> If it does not, I try the standard-procedures to fix it, if this does
>> not help I switch the distro.
> And first of all, don't care that much about latency, because latency
> very seldom is an issue, just jitter could become an issue.

I agree, that audible jitter would be an absolute show-stopper.

Anyway I never heared such effects in any recordings I made in the last 
7-8 years. I only had audible effects in the form of xruns and in 
test-scenarios with insane settings or with alpha-software or a severely 
misconfigured system.

> Cheers!
> Ralf

More information about the Ubuntu-Studio-users mailing list